The Advanced Television Systems Committee Vestigial Sideband (ATSC VSB), U.S-oriented terrestrial waves digital broadcasting system, is a single carrier scheme and uses field synchronizing signal by 312 segment unit. Accordingly, reception performance is not good in poor channels, especially in a doppler fading channel.
FIG. 1 is a block diagram showing a conventional transmitter of the ATSC VSB. The digital broadcasting transmitter of FIG. 1 forms and transmits a dual stream by adding a robust data to a normal data of the existing ATSC VSB system according to ‘ATSC Digital Television Standard (A/53B)’ of Enhanced Vestigial Sideband (EVBS) system.
As shown in FIG. 1, the robust data in the digital broadcasting transmitter is processed by a robust data processor (11), and the robust data processor (11) has a Reed-Solomon (RS) encoder (11-1), a data interleaver (11-2) and a packet formatter (11-3). The packet formatter (11-3) has a packet identifier (PID) inserter (not shown) and a ½ or ¼ rate duplicator (not shown). Robust data processed by the robust data processor (11) is multiplexed with a normal data by a multiplexer (MUX) (12).
The data output in the multiplexer (12) is randomized through a randomizer (13) and passes through an RS encoder (14) and an interleaver (15) in the form of a concatented code to correct errors generated by the channel. In addition, a symbol processor (16) performs enhanced coding for the robust data, a de-interleaver (17) deinterleaves it before reconstructing RS parity, and an RS parity deleting part (18) deletes RS parity to be compatible with the existing system. The data whose the RS parity is deleted is input to a VSB transmitter (19). The VSB transmitter (19) includes an RS encoder (19-1), a data interleaver (19-2), a Trellis encoder (19-3) and a multiplexer (19-4) according to the structure of a general VSB transmitter and performs RS encoding, data interleaving, 12 Trellis interleaved encoding, insertion of a synchronizing signal and a pilot, VSB modulation and up-convertor.
The above-mentioned conventional digital broadcasting transmitter transmits normal data and robust data in one channel as a dual stream scheme. The robust data is pre-processed by the robust data processor, in detail the pre-processing is performed by the RS encoder (11-1), the interleaver (11-2) and the packet formatter (11-3) with the PID inserter (not shown) and the duplicator (not shown) so that the Moving Picture Experts Group-2 transport stream (MPEG-2 TS) is generated.
The robust data pre-processed by the robust data processor (11) is multiplexed with the normal data by the multiplexer (MUX) (12) and is randomized by the randomizer (13) and the randomized data is outer-coded by the RS encoder (14) of an outer coder, and the outer-coded data is dispersed by the interleaver (15). In addition, the robust data is enhancedly coded by the symbol processor (16), and passes through the deinterleaver (17) for performing symbol-to-byte conversion and data interleaving for compatibility with the existing system and the parity delete (18).
Later, as performed in the existing VSB transmitter, RS encoding, data interleaving, 12 Trellis interleaved encoding, insertion of a synchronizing signal and a pilot, VSB modulation and so on are carried out.
FIG. 2 shows a data format of the data output by the multiplexer (12). In FIG. 2, the normal data and the robust data are arranged at certain intervals so that the normal signal and the robust signal after Trellis encoding are distributed at regular intervals.
The U.S-oriented terrestrial waves digital television system of FIG. 1 transmits in the dual stream by adding the robust data in the normal data of the existing ATSC VSB system, so the existing normal data and the robust data are transmitted altogether.
However, the U.S-oriented terrestrial waves digital television system of FIG. 1 has a problem that in spite of dual stream transmission with the robust data, poor transmission performance at multipath channels on transmitting the existing normal stream is not almost improved.